What is happening to me?

UPDATE: I realized later on through the day that I actually HAD been dreaming about sexual things before this happened, but I had no memory of it until much later.

I was half awake this morning and I felt a twitching/pulsing sensation in my vagina, towards the opening. I have never felt this before. I wondered if it was an orgasm in my sleep but I was not having a sexually erotic dream. I googled it and couldn't find a direct answer. Do you know what it is? I'll give you a bit more background on me.

I'm 26, raised in a religious home that taught abstinence. I didn't know what mastubation was, so rather than ask a parent, I thought I should suppress it. I didn't masturbate from ages 13-21. But even when I did, I did not experience orgasms because I didn't know how to touch myself. I learned about clitoral stimulation from my boyfriend when he started rubbing down there about 6 months ago. That made me orgasm. He and I have had a fumbled version of intercourse 3 times, but not for 3 months now. I have PCOS and am not taking anything to get a period so I haven't had one for 2 months. I was on birth control but it gave me nocturnal panic attacks so I stopped. I take one antidepressant every day.

I hope that helps you figure this out. I want to know what it is. The internet said anything from harmless sleep gasms to vaginismus.